Lifting-jack.



UNI @TAT PAT T FTCE.

ISAIAH E. HINDMAN, OF BOSS TOWNSHIP,

ALLEGHENY COUNTY, AND GEORGE E.

FEEED, OF BEN AVON, PENNSYLVANIA, ASSIGNORS TO THE DUFF MANUFAC- TURING COMPANY, OF NORTH SIDE, PITTSBURGH, PENNSYLVANIA, A CORPORA- TION OF PENNSYLVANIA.

LIFTING-JACK.

Specification of Letters Patent.

Patented Aug. '7, 1917.

To all whom it may concern:

Be it known that we, ISAIAH E. HINDMAN and Gnonen F. FRnnD, both citizens of the United States, residing, respectively, at Ross Township and Ben Avon, both in the county of Allegheny and State of Pennsylvania, have invented a new and useful Improvement in Lifting-Jacks, of which the following is a full, clear, and exact description, reference being had to the accompanying drawings, forming part of this specification, in which- Figures 1 and 2 are sectional elevations of a jack embodying our invention, the section of Fig. 1 of Fig. 2; and the section of Fig. 2 being taken on the line II-II of Fig. 1.

Fig. 3 is a detail View, partly in plan and partly in horizontal section, and showing a portion of the worm shaft, and also the pawl and lever socket, and

Fig. 4 is a section on the line IV-IV of Fig. 3.

Our invention has relation to lifting jacks, and more particularly to quick-pitch worm jacks of that type wherein the angle of the thread of the driving worm is sufiiciently great to permit the worm gear to drive the worm when under a load. It is well known that the greater the angle of the worm thread, the more efficient will be the jack; but in jacks of this character there is'diiii culty in holding up the load between successive strokes of the operating lever in raising, while permitting lowering when desired.

Our invention is designed to overcome this diiliculty and to provide a jack having a mechanical clutch brake device which will hold the load during lifting, but which will allow the same to be lowered, if desired.

A further object is to provide a jack of this character which is comparatively simple in its construction, safe and efficient in its operation, and in which there will be no possibility of the load sinking back when the raising action is stopped.

Our invention will be best understood by reference to the accompanying drawings, in which we have shown a preferred embodiment of our invention, and which will now be described, it being premised, however, that various changes can be made in the being taken on the line I-I' details of construction, arrangement, and combination of the several parts without departing from the spirit and scope of our invention as defined in the appended claims.

In these drawings the numeral 2 desigr' nates the frame of the jack having suitable housing portions 3 and 4t for the worm and worm gear. 5 designates the worm which drives a worm wheel 6 fastened to a shaft 7 carrying a rack pinion 8 whose teeth mesh with the rack teeth 9 on the lifting bar 10 which carries the load.

The shaft 11 of the worm 5 is journaled in suitable bearings 12, and is extended at one end to form a shaft to which is secured a ratchet wheel 13. 14 designates the socket of the actuating lever, this socket having a bifurcated end portion embracing the ratchet wheel 13. 15 is an oscillating double pawl hung between the bifurcations of the lever socket 14. on the pin 16. This pawl is formed with one set of teeth 17 adapted, in one position of the pawl (shown in full lines in Fig. 1) to engage with the teeth of ratchet wheel 13, and with another set of teeth 18 adapted, in another position of the pawl (shown in dotted lines in Fig. 4) to engage with teeth 19 which are formed on the periphery of a brake wheel 20. This brake wheel is seated in a counterbore 21 of the casing between the ratchet wheel 13 and the worm 5. It is formed with the internal tapered slot 22, and a clutch roller 23 is seated between the 'wall of said slot and the shaft 11. This roller is arranged to bind in the smaller end of the slot 22, but becomes loose at the larger end portion of said slot. 24 is a spring seated behind the roller 23. When the shaft 11 turns in the raising direction indicated by the arrow, the roller 23 tends to be carried toward the larger part of the tapered slot, allowing all parts to run freely. This free movement of the roller is assisted by the key 25 which is in shaft 11. When the shaft 11 turns in the raising direction, the key 25 acts against the shoulder 26, in brake wheel 20. This revolves the brake wheel and shaft in the same direction and the roller 23 cannot bind in slot 22. When, however, the shaft 11 starts to turn in the reverse or lowering direction, the roller is carried toward the narrow end of the slot, causing the brake wheel to bind between the walls of the counterbore 21 and the roller, thus effectively checking further movement in this direction.

During the raising operation the pawl 15 is in the position shown in full lines in Fig. 4. If it is desired to lower the load, the pawl is reversed to bring its teeth 18 into engagement with the teeth 19 of the brake wheel 20. The latter also has-a shoulder26 adapted to engage the key 25 of the shaft '11 at the narrow end of the slot 22. Then the pawl is thus reversed this shoulder will engage this key and thus cause the brake wheel and the shaft to be rotated in the lowering direction, the clutch roller-19 being at the same time prevented from gripping.

The pawl 15 is set manually to the position desired, and is held in this set positionby any suitable means such as the springpressed dog 27, which engages the depression 28 of the pawl (see Figs. 3 and 4). 29 designates a thrust bearing of any suitable character for taking the thrust of the worm. In the form shown, this bearing consists of a plurality of hardened plates seated between an end of the worm and the abutment 30 on the jack casing.

It will readily be seen that during the lifting of a load the brake wheel will move as fast as the worm shaft, thus preventing "the clutch from taking a grip sufficient to retard the movement of such shaft,'but that the clutch will immediately become effective to prevent backward movement as soon as the raising operations are stopped.

The advantages of our invention will be apparent, since it provides an extremely 5 simple and easily operated jack of the type described. The load is efiiciently heldduring raising operations, but by a simple reversal of the. pawl can be lowered under control, as may be desired.

' We claim: 1

1. In a lifting jack, the combination of a lifting bar,a quick-pitch worm eared to said bar to actuate the same, a ratchet mem- -b'er fixed to the worm shaft, an actuating lever having a reversible pawl adapted in one position to engage the teeth of said ratchet member, a brake member loosely surrounding said shaft and having teeth adapted'to be engaged-by the pawl in its reverse I position,and a single acting clutch device arranged to connect the brake memberwith the worm shaft when the latter turns in a load-lowering direction, together with means whereby the brake member may be caused -to actuate said shaft when engaged by said pawl, substantially as described.

2. In a lifting ack, a lifting bar, a quickpitch worm geared-t0 said lifting bar, said worm having its shaftprovided with two ratchet members, one of said ratchet mem' bers being fixed to sai'dshaft, and the other of said members having a single-acting clutch connection with the shaft, an operating lever, and a reversible pawl carried by the operating lever and adapted to alternately engage the two ratchet members, one of said ratchet members being arranged to form a brake, andmeans whereby the last named ratchet member, when actuated by its pawl, is caused to rotate said shaft in a lowering direction, substantially as described.

3. In a lifting jack, a lifting bar, aquick pitch worm geared to said bar, a ratchet wheel fixed to the shaft of said worm, a

brake wheel loosely mounted on said shaft,

said brake-wheel having an internal single acting clutch adapted to lock the brake wheel to the shaft during the lowering movement of said shaft under its load, and. also having means to actuate said shaft when the brake wheel is actuated by the pawl, an operating lever, and a reversible pawl carried by said lever and adapted to engage either the ratchet -wheel or the brake wheel, substantially as described.

4. In a lifting jack, a lifting bar, a quick:

pitch worm geared to said bar, a brake wheel loosely mounted on said shaft and having ratchet teeth, said wheel also having an internal clutch slot terminating in a shoulder, a clutch roller movable in said slot, the worm shaft having a key arranged to engage said shoulder, and a lever member for actuating said shaft, said member having means for operatively disengaging the said shaft, and for operatively engaging the teeth of the brake wheel, substantiallyas described. I

5. A lifting jack, comprising a lifting bar, a worm geared to said bar, a brake member for locking the worm against movement under the action of the load, a ratchet wheel connected to the worm, and a reversible pawl having one portion for engagement with the brake member, and. another portion for engagement withsaid ratchet member;- substantially as described.

In testimony whereof, we have hereunto set our hands.

I. E. HINDMAN. GEORGE F. FREED.

Witnesses:

. GEO. A. YOUNG,

DANIEL WEISSENSTEIN.

I -Copies of this patent may be obtained for five cents each, -by addressing the Commissioner IoI'IPatents'j Washington, D. G. 

